A pressure monitoring device of the general type under consideration is known as a “governor”. It is used as a device that monitors the air pressure in a tank connected to an input air connector of the governor and outputs pressure signals as pneumatic signals to an air compressor. The compressor is provided for pumping air in an operation mode, which may be called the “on-load-state”, and for not pumping air in a non-operation mode, which may be called the “off-load-state”. This non-operation mode can be an idle state, in which the compressor is not switched off, or it can be a switched-off state.
GB 1,006,806 A, U.S. Pat. No. 3,834,837, U.S. Pat. No. 3,545,887 describe governors of the general type under consideration, which are mechanical devices comprising mechanical parts. In general, a governor is used to limit the pressure in the tank; if a pressure limit is reached or exceeded, the governor connected to the pressurized air tank detects this state and outputs an OFF-load signal to the compressor in order to switch it into its off-load-state.
A governor comprises a spring mechanism to compare the pressure received in the input air connector with a spring force of the spring mechanism. However, debris in the air compressor or inconsistent venting of the governor signal, weak springs or stuck unloader mechanisms may lead to failures in outputting the OFF-load signal.
Further problems may arise when a leak is present in the signal line from the governor to the compressor. This may cause the governor to become slow or sluggish during the vent cycle and may lead to failure in the air compressor unloader mechanism.